DESCRIPTION

These functions may be used to obtain explanations for errors returned
by the fdopen(3) system call.
explain_fdopen
const char *explain_fdopen(int fildes, const char *flags);
The explain_fdopen function is used to obtain an explanation of an
error returned by the fdopen(3) system call. The least the message
will contain is the value of strerror(errno), but usually it will do
much better, and indicate the underlying cause in more detail.
The errno global variable will be used to obtain the error value to be
decoded.
This function is intended to be used in a fashion similar to the
following example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
fprintf(stderr, "%s\n", explain_fdopen(fildes, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fdopen_or_die(3) function.
fildes The original fildes, exactly as passed to the fdopen(3) system
call.
flags The original flags, exactly as passed to the fdopen(3) system
call.
Returns:
The message explaining the error. This message buffer is
shared by all libexplain functions which do not supply a buffer
in their argument list. This will be overwritten by the next
call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return
buffer across all threads, and many other functions in this library.
explain_errno_fdopen
const char *explain_errno_fdopen(int errnum, int fildes, const char
*flags);
The explain_errno_fdopen function is used to obtain an explanation of
an error returned by the fdopen(3) system call. The least the message
will contain is the value of strerror(errnum), but usually it will do
much better, and indicate the underlying cause in more detail.
This function is intended to be used in a fashion similar to the
following example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
int err = errno;
fprintf(stderr, "%s\n", explain_errno_fdopen(err, fildes, flags));
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fdopen_or_die(3) function.
errnum The error value to be decoded, usually obtained from the errno
global variable just before this function is called. This is
necessary if you need to call any code between the system call
to be explained and this function, because many libc functions
will alter the value of errno.
fildes The original fildes, exactly as passed to the fdopen(3) system
call.
flags The original flags, exactly as passed to the fdopen(3) system
call.
Returns:
The message explaining the error. This message buffer is
shared by all libexplain functions which do not supply a buffer
in their argument list. This will be overwritten by the next
call to any libexplain function which shares this buffer,
including other threads.
Note: This function is not thread safe, because it shares a return
buffer across all threads, and many other functions in this library.
explain_message_fdopen
void explain_message_fdopen(char *message, int message_size, int
fildes, const char *flags);
The explain_message_fdopen function may be used to obtain an
explanation of an error returned by the fdopen(3) system call. The
least the message will contain is the value of strerror(errno), but
usually it will do much better, and indicate the underlying cause in
more detail.
The errno global variable will be used to obtain the error value to be
decoded.
This function is intended to be used in a fashion similar to the
following example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
char message[3000];
explain_message_fdopen(message, sizeof(message), fildes, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fdopen_or_die(3) function.
message The location in which to store the returned message. If a
suitable message return buffer is supplied, this function is
thread safe.
message_size
The size in bytes of the location in which to store the
returned message.
fildes The original fildes, exactly as passed to the fdopen(3) system
call.
flags The original flags, exactly as passed to the fdopen(3) system
call.
explain_message_errno_fdopen
void explain_message_errno_fdopen(char *message, int message_size, int
errnum, int fildes, const char *flags);
The explain_message_errno_fdopen function may be used to obtain an
explanation of an error returned by the fdopen(3) system call. The
least the message will contain is the value of strerror(errnum), but
usually it will do much better, and indicate the underlying cause in
more detail.
This function is intended to be used in a fashion similar to the
following example:
FILE *fp = fdopen(fildes, flags);
if (!fp)
{
int err = errno;
char message[3000];
explain_message_errno_fdopen(message, sizeof(message),
err, fildes, flags);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);
}
The above code example is available pre-packaged as the
explain_fdopen_or_die(3) function.
message The location in which to store the returned message. If a
suitable message return buffer is supplied, this function is
thread safe.
message_size
The size in bytes of the location in which to store the
returned message.
errnum The error value to be decoded, usually obtained from the errno
global variable just before this function is called. This is
necessary if you need to call any code between the system call
to be explained and this function, because many libc functions
will alter the value of errno.
fildes The original fildes, exactly as passed to the fdopen(3) system
call.
flags The original flags, exactly as passed to the fdopen(3) system
call.